It's not a constructive conversation, really, and if anybody has the energy to go down that rabbit hole again, will probably devolve into a debate about the meaning of "clean".
But the way to tell is to compare times on classic climbs. Though they aren't climbing Alpe d'Huez this year, a look at the best times through the years shows that modern racers do not match the times of Pantani or Armstrong during the heavy doping era
https://cycling-passion.com/top-200-...s-alpe-d-huez/